Foundation stones and long through stones
The explanations in the section "Design" show that the retaining walls made of dry masonry are particularly under stress in the lower third of their height. In this area, the following points must be taken into account during construction:
If the resulting force cuts the footing line in the foundation area very far out, there is a danger that foundation stones will be pressed into the soil. The foundation stones sink in towards the outside and a bulge is formed (Fig B below). This damage is often observed when the foundation stones are too small or the bearing capacity of the soil is not high enough.
As a countermeasure, sufficiently large foundation stones are to be installed (as binders and if possible protruding). In the lower third of the wall height, more long through stones are to be installed than in the remaining wall height (Fig C below). See also the SIA Merkblatt 2053, paragraph 6.3.1. In addition, the rule applies that the resulting force should intersect the foot line of the trapezoidal cross-section in the middle third.
The resulting force acting far out against the face of the wall can cause very narrow and high stones installed as runners to tilt. Here, too, undesirable movements and deformations of the masonry can result (Fig E below). This effect can be prevented if (especially in the lower third of the wall height) sufficiently long through stones are placed (Fig F below).
The same applies if a failure from tilting and sliding occurs (cf. section "Dimensioning"). Here, too, the installation of sufficiently long through stones can prevent failure of the dry masonry in the base area. In this regard, see also SIA Merkblatt 2053, paragraph 6.3.1.